Nutrition and Your Health:
Dietary Guidelines for Americans

PART F: RESEARCH RECOMMENDATIONS

GENERAL OVERARCHING RESEARCH RECOMMENDATIONS

Investigate the impact of following adult-based dietary guidelines
on nutrient intake and health or metabolic effects in children
and later in life. Determine the impact of establishing dietary
guidelines in childhood on dietary intakes and patterns later
in life.

Rationale: Research on the effectiveness of
using adult-based dietary guidelines for children is limited.

Rationale: This report relied heavily on observational
studies that assessed the relationship of foods to health outcomes.
Available trials typically evaluated the relationship between
specific nutrients or food components rather than whole food
groups or diets.

Establish a system for ongoing systematic reviews on key nutrition
and physical activity topics relevant to dietary guidance for
the general public.

Rationale: A system to conduct ongoing evidence-based
reviews on topics relevant to dietary guidance for the general
public will streamline the tasks for the next Dietary Guidelines
Advisory Committee and is in keeping with the Federal Data Quality
Act.

Develop a scientifically valid definition for "nutrient density"
that could be useful on the food label. Determine what criteria
are necessary for foods to meet this definition.

Rationale: Over the past decade, a widespread
concern has been that some foods may be classified as less nutrient
dense than others and these foods may be eaten at the expense
of other foods that are, by comparison, better sources of essential
nutrients. To assist consumers in making wise food choices,
a method is needed to convey the nutrient density of a food
on the label.

Conduct studies to determine the barriers for complying with
the Dietary Guidelines among children, low-income populations,
and various ethnic groups. Identify various mechanisms to motivate
individuals to change their eating behaviors and habits.

Rationale: Currently, compliance with the
Dietary Guidelines is poor. There is a need to understand what
barriers prevent compliance and how to motivate individuals
to change their eating behaviors and habits and increase compliance
with the Dietary Guidelines.

Develop and test both individual-based and population-based
interventions designed to implement Dietary Guidelines.

Rationale: Achieving all Dietary
Guidelines may be challenging. For instance, it might be difficult to increase
the intake of key nutrients without inadvertently increasing
calorie consumption. Additionally, the extent to which increased
physical activity enhances the ability to meet nutrient needs
has not been assessed. Strategies that assist the general public
and health care professionals will be needed, along with evaluation
of those strategies.

SPECIFIC RESEARCH RECOMMENDATIONS

Establish the effect of various food components (e.g., flavonoids,
other antioxidants, citrate) on metabolism and indicators
of health.
Develop food composition databases to accurately assess the
intake of these food components and conduct human studies
to determine
the biological function of these dietary constituents.

Rationale: A growing body of scientific evidence suggests that
food components may affect the risk of chronic disease, but data
are lacking on the intakes of these dietary constituents, their
biological function, and their health effects independent of nutrients.

Investigate the dietary requirements of vitamin D in vulnerable
groups (i.e., older adults, house-bound individuals, and those
with dark skin). This research requires the development of a database
for the vitamin D content of foods, estimates of usual vitamin
D intake from foods, determination of the indicators of vitamin
D status and the effect of latitude and seasons on those indicators,
and the vitamin D intake required to maintain adequate status
in various age and ethic groups.

Rationale: Vitamin D is supplied mainly by synthesis in the skin
with sunlight exposure, and this synthesis may be adequate in
fair-skinned people who are active outdoors, especially in southern
States. Older, less active people who stay indoors and those with
darkly pigmented skin are more prone to having vitamin D insufficiency.
The National Health and Nutrition Examination Survey, which monitors
vitamin D status only in northern latitudes during the summer
months, may not adequately detect insufficiency.

Investigate the vitamin E requirements of individuals consuming
various types and amounts of dietary fat, the bioavailability
of vitamin E from various food sources, and the effect of vitamin
E status on the risk of chronic disease. Develop a comprehensive
nutrient database for the vitamin E content of foods.

Rationale: Current data suggest that the vitamin E intakes of
Americans are inadequate compared with the Recommended Dietary
Allowances. However, the health consequences of chronically low
vitamin E intakes are uncertain.

Investigate the relationship between added sugar intake and
various health outcomes, including BMI (or obesity) and type 2
diabetes.

Rationale: There is a paucity of longitudinal studies that assessed
the long-term effects of added sugars on BMI and other health
outcomes. Long-term studies, and if possible, dose-response trials
are needed to better understand the relationship between added
sugar consumption and health in adults and children.

Investigate the relationship between portion size and BMI
(or obesity).

Rationale: There is a lack of longitudinal studies that assessed
the long-term effects of differing portion sizes on BMI and obesity.
It is important to find out whether a campaign to limit portion
size would be effective in the prevention of overweight and obesity.

Investigate the relationship between the pattern of food intake
(i.e., skipping breakfast or other meals or the frequency of food
consumption) and BMI (or obesity).

Rationale: The effect of skipping meals or frequent snacking
on BMI (and obesity) is not clear. Current data are poor and short
term. It is important in designing strategies for managing body
weight to have a better understanding of the role of pattern of
food intake on body adiposity.

Investigate the relationship between dietary glycemic load
and BMI.

Rationale: The effect of glycemic response on BMI is uncertain,
because evidence from observational studies is inconsistent and
because there are few randomized trials. Randomized trials are
required to establish whether the dietary glycemic load is an
important factor in regulating body fat and altering the risk
for type 2 diabetes.

Rationale: The Institute of Medicine (IOM)
recommendations for acceptable macronutrient distribution range
(AMDR) provide a wide range of carbohydrate, protein, and fat
intakes. Various ratios of macronutrients within the AMDR need
to be tested in long-term studies to determine their effects
on energy homeostasis and regulation of body weight. Also, nutrient
adequacy at the extremes of AMDR (e.g. total protein intake
of 35 percent of calories) needs to be assessed.

Investigate the effect of various types of fatty acids (i.e.,
saturated fatty acids, trans fatty acids, α-linolenic acid) on
the incidence and prevention of cancer.

Rationale: There is limited evidence on the effect of specific
fatty acids on human breast cancer, prostate cancer, and other
cancers.

Determine the optimal n-6 to n-3 fatty acid ratio in relationship
to health outcomes; investigate the conversion factor of α-linolenic
acid to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
and how n-6 intake competes with that conversion rate; compare
the effects of EPA and DHA versus fish on lipid metabolism and
other health outcomes; and determine the health effects of fish
consumption on type 2 diabetes and cancer.

Rationale: There are few studies comparing
the effects of various n-6 to n-3 fatty acid ratios on lipid
metabolism and other health outcomes. The impact of these polyunsaturated
fatty acids on health needs to be examined in long-term studies
of adults and children.

Compare the effects of various sources of trans fatty acids
on lipid metabolism and health outcomes.

Rationale: Research is needed to determine whether differences
exist in the health effects of industrial versus animal sources
of trans fat.

Investigate the effects of stearic acid intake on lipid metabolism
and health.

Rationale: Stearic acid has attracted interest
as a substitute for trans fatty acids in prepared foods
that require a solid fat. Stearic acid offers the functional
properties needed for these foods, but the question arises of
how it affects blood lipid values and indicators of cardiovascular
disease.

Investigate the health benefits derived from the consumption
of cereals, fruits, and/or vegetables; ascertain the biological
mechanism whereby cereals, fruits, and vegetables alter disease
risk; and determine the effects of fiber from these food sources
on health (i.e., obesity and comorbidities).

Rationale: Clinical trials, and if possible, dose-response studies
are needed to expand our understanding of the health benefits
associated with cereals, fruits, and vegetables and to determine
whether those benefits are related to the fiber content of these
foods and/or other components.

Investigate the implications of the intake of bottled water
on fluoride intake and on health outcomes (especially oral health).

Rationale: Most bottled water is not fluoridated.
With the dramatic increase in consumption of bottled water,
there is concern that the public may not be getting enough fluoride
for maintenance or oral health.

Compare the effects of foods and beverages that contain added
sugars and those that naturally contain sugar on body adiposity
and other indicators of health in children and adults.

Rationale: Studies are needed to determine the impact of different
types of sugar on human health.

Rationale: There are very few studies that compare sources of
calcium and their impact on bone health, energy metabolism, insulin
resistance, and blood pressure.

Investigate the role of increased total fluid intake as a
means to prevent chronic diseases.

Rationale: The IOM report identified a few studies suggesting
that increased fluid consumption is associated with a reduced
risk of bladder cancer, urinary tract infections, kidney stones,
and colon cancer. However, this evidence was insufficient to make
recommendations on fluid intake.

Conduct trials that assess the effects of salt intake on
clinical outcomes other than blood pressure.

Rationale: Numerous studies have documented a direct relationship
between salt intake and other outcomes, including urinary calcium
excretion and left ventricular hypertrophy. In view of these findings,
trials with clinically relevant outcomes, such as bone mineral
density or left ventricular mass, are needed.

Rationale: A consistent body of evidence from observational studies
indicates that increased intake of potassium from foods is associated
with greater bone mineral density and with evidence of reduced
bone turnover. Data from small trials also have documented that
increased intake of potassium reduces bone turnover.

Conduct dose-response trials that test the main and interactive
effects of sodium and potassium intake on blood pressure and other
clinically relevant outcomes.

Rationale: There remains a need for dose-response trials, particularly
for potassium, that span a clinically relevant range of dietary
intake. Also, the interactive effects of sodium and potassium
are of considerable interest.

Investigate the relationship between moderate alcohol consumption
and obesity.

Rationale: The data on the relationship between alcohol consumption
and weight gain and/or obesity are inconclusive. Consumption of
one or two drinks per day is associated with increased caloric
intake. However, there is no apparent association between consuming
one or two drinks a day and obesity.

Investigate the impact of adding calorie information to
the labels of alcoholic beverages, including whether, for
educational
purposes, it would be sufficient to include only calories
(i.e., not nutrients).

Rationale: The caloric content of alcoholic beverages varies widely.
Consumers do not have easy access to this information. Since alcoholic
beverages provide calories and few nutrients, a more detailed
label may not contribute useful information.

Investigate the impact of banning alcohol advertising when
and where it might increase underage drinking (e.g., during college
sports events).

Rationale: Underage drinking is a major problem
in the United States, and effective strategies to decrease the
problem are needed.

Investigate the impact of unified Federal messages on alcohol
and health through increased collaboration across agencies or
consolidation of authority under one Federal agency.

Rationale: With diverse groups responsible for messages on ethanol
and health and with a variety of audiences, a consistent message
has been difficult to achieve. Increased collaboration or consolidation
would provide a unified message and have the potential to increase
knowledge and promote healthful attitudes and behaviors related
to alcohol consumption.

Investigate the effects of different types of cleaning on
various surfaces. This research requires quantification of the
type and counts of bacteria likely to be present on the surface
before and after cleaning.

Rationale: Food safety guidance needs to be continually updated
as food consumption and preparation practices change and new pathogens
emerge or adapt and change. Currently, insufficient data exist
to clearly quantify the types and counts of bacteria likely to
be present on surfaces before and after cleaning; such information
is needed to set priorities for consumers.

Conduct research to improve methods to assess the risk of
food safety (or the health benefits of a food) versus other factors
(i.e., environmental contaminants of fish).

Rationale: As scientific technology grows, risk assessment methods
become more important in the complex task of prioritizing the
public health issues and communicating key safety messages. When
providing food safety information to consumers, it is important
that they understand the message. This requires knowledge of the
risk assessment of food safety versus other factors (i.e., environmental
contaminants in fish). This knowledge allows the consumer to prioritize
various messages, which can be weighed, based on science. In this
way, the information critical to food safety can be conveyed so
that the consumer does not have an inordinate number of other
issues to consider.

Conduct consumer research to evaluate food safety messages
and corresponding changes in behavior.

Rationale: Changing lifestyles have increased the need to assist
consumers in recognizing the symptoms and sources of foodborne
disease so that corrective action can be taken.